Ian:

Since you’re about to become a father, I think it’s time for us to have “the talk”. The one where we prepare you for empty chasm of harmonic complexity in which you’re going to live for the next 6-14 years. Right now, you’re probably under two incorrect impressions:

1. “My child and I are not going to listen to silly kids music, he/she is going to be raised only on [The Beatles / Radiohead / Bach / insert your own dreams and aspirations here], and I will fully avoid exposure to songs about ladybugs who eat ice cream.”
2. “I know kids music is simple and dull, but it can’t be that bad.”

Regarding (1). You will try this, yes. In fact this approach will last for a deceptively long time, in that for the first two years of life your child will have no real opinions and will not have any concept of other children, so sure, it’s all Beatles and Breaking Bad when you’re up at 3am.

But much like we tried to minimize Kelsey’s exposure to princesses and my-little-ponies, only to find that society kicks in around age 2 and sweeps in late at night to replace everything in her room with its princess-colored equivalent (yes, incidentally, “princess” is a color), once your child gets her first taste of Raffi and Kinderwhatever, there is no going back. This will occur around the same time that she achieves “free will”, i.e. “the ability to throw food/juice/feces until she gets what she wants”. What she wants, it turns out, is Raffi and/or “whatever the big girls are listening to”. And since “the big girls” are only 3, the latter is also Raffi. You will give in by age 2.04.

Regarding (2). Oh, yes, it can be. Let’s forget about good and bad for a moment and just talk about objective factors… you probably expect that the harmonic vocabulary of kids music is slightly reduced, like maybe they cut back on the augmented chords a little and don’t want to scare kids with too many bIII’s. But surely it still vaguely resembles the chord palette of the pop and rock that inspired modern kids music? Nay. Nay nay nay.

Not only will you go three years without hearing a non-diatonic chord, you will go three years without hearing a minor chord. And this leaves us with precisely three chords, namely I, IV, and V. You will get to a point where your ears perk up at V7’s and I7’s. When I first heard a secondary dominant in Raffi’s “Baby Beluga” (to this day the only non-diatonic chord I’ve heard in a “kids music” song), I lost my fucking mind with pure glee. It was as close as I’ll experience to when my parents’ generation unwrapped their copies of Sgt. Pepper’s LHCB and drifted into rich, sophisticated, musical bliss. Only in my case, it was over a completely predictable, uninteresting secondary dominant played on what is obviously a first-generation Casio keyboard.

Raffi – Baby Beluga

[G]Baby beluga, [D]baby beluga
[E]Sing your little song, sing for all your friends
We [A7]like to hear you...

(Note it's in D, lest the IV → I → II → V appear as a somewhat-more-interesting I → V → VI → II.)

BUT WAIT. There is some good news. That good news comes in precisely two forms: (1) former rock stars who clean up, have kids, and re-invent themselves as children's artists, and (2) Disney songs.

Regarding (1). You will find no shortage of folks in this category; They Might Be Giants, Jack Johnson, and Ziggy Marley have all gotten in on this action. If you prefer the opposite but related phenomenon - covers of rock classics intended for kids - you should know that "Dreamin' with Def Leppard" is an actual album. But up here in the PNW, we have a solid favorite in this category: Caspar Babypants, formerly known as Chris Ballew, and by "known", I mean of course you don't know his name, but you know him as the singer from the Presidents of the United States. Caspar Babypants is a respite from the harmonic vacuum of the babyverse, and even the mixing/mastering is much more reminiscent of "rock" than "kids". Since you know I judge artists not entirely, but almost entirely, on what percentage of their songs include a I → I7 → IV → iv, I will introduce you to Caspar Babypants with a personal favorite, "$9.99":

Caspar Babypants – $9.99

This [D]little soul of mine is [G]nine ninety nine
and [D]if you've got some thread then you can [A]fix me
I'm [D]torn old and [D7]pale and [G/B]I am for [Gm/Bb]sale
[D]what I need is [A]for someone to [D]pick me [G][D]

Regarding (2). The Disney train is, of all the baby-related trains, the train I most strongly encourage you to board as early as possible. I'll mention first that so far I've only talked about the harmonic simplicity of kids' music. Neither of us are audiophiles, so we get less hung up on tone than some might, but by any objective criteria, most kids songs are thrown together pretty hastily and don't exactly shout "quality". By analogy, without really making a subjective judgement, whether you like animated movies or not, one can clearly say that more cratfsmanship went into "Toy Story" than into an episode of "Dora The Explorer". Similarly, the aforementioned Raffi song is one of the most popular kids songs of all time (for some reason it amuses me that Wikipedia says that Baby Beluga "...is considered by many to be his greatest hit." I picture a thoughtful gathering of musical critics discussing the symbolism of the waves rolling in and out, which of course is not symbolic, because it's actually about a whale). But in any case, it seriously sounds like the MIDI track over which one would eventually play the actual track. In contrast, even Disney songs with no harmonic complexity, and only I/IV/V, are usually awesome. E.g. "Kiss The Girl":

Sebastian the Crab – Kiss The Girl

[G]Shalalalala [C]my oh my looks like the
[G]boy too shy ain't gonna [D]kiss the girl
[G]Shalalalala [C]ain't that sad it's such a
[D]shame, too bad, you're gonna [G]miss the girl

In fact, an oddly popular cover of this song added some vi's, bringing the total number of unique chords to four, and I wasn't a fan... i.e., I just wanted the I/IV/V back.

Ashley Tisdale – Kiss The Girl

(It's in C; I'm writing in G for an apples-to-apples Ashley-vs-Sebastian)

[Em]Shalalalala [C]my oh my looks like the
[G]Boy's too shy ain't gonna [D]kiss the girl
[Em]Shalalalala [C]ain't that sad it's such a
[D]Shame, too bad, you're gonna [G]miss the girl

Point being: Disney got it right the first time. And of course, in the grand scheme of kids music, you can count on Disney for both production quality and musical effort, so I'd estimate the average harmonic entropy of Disney songs not only towers above that of most kids music, but sits right around most rock, i.e. in that comfortable ideal between pop and jazz.

If, for example, you're me, and you have an uncomfortable attraction to I → I7 → IV → iv, Disney delivers:

Ariel the Mermaid – Part of Your World

Up where they [F#]walk, up where they [F#7]run
Up where they [B]stay all day in the [Bm]sun          
Wanderin' [F#]free, wish I could [C#]be
Part of that [F#]world

And no one will say I didn't put my money where my mouth is wrt this song:

Dan Morris – Part Of Your World

But lest you should think it's not so much Disney music I'm advocating but '80s mermaids (mermaids did seem more popular in the '80s, no?), modern Disney music has IMO kept up the pace. And as any 2014 parent knows, "modern Disney music" only really means "songs from Frozen", and in fact mostly only "Let it Go". Fortunately, "Let it Go" has a shitload going on. I'm writing here in G, it's actually in Ab.

First we have what appears to be a very standard vi → IV → V → ii, but it actually alternates between resolving to ii and resolving to II, cleverly starting with a sus in both cases (iisus then IIsus) such that you have to listen a couple times to see that it's different (it does all this in the piano intro too). I don't know of other songs with this property (repeating phrases than end in x and X):

Elsa the Ice Queen – Let It Go (verse)

The [Em]snow glows white on the [Cadd9]mountain tonight
Not a [D]footprint to be se[Am]en
A [Em]kingdom of iso[Cadd9]lation, and it
[D]looks like I'm the Queen[A]

Then in the chorus, there's a bIII that at first was too jazzy for me, because it's actually going iii → bIII (another transition I can't say I've seen before), but it totally grew on me, and now I think it's even more awesome than the average bIII, which is already pretty awesome.

Elsa the Ice Queen – Let It Go (first chorus)

[G]I don't care[D], what they're [Em]going to sa[C]y
Let the [Bm]storm rage [Bb]on, the [C]cold never bothered me anyway

And if you think I had trouble accepting the iii → bIII, I really fought against the IV → iv → iii → bIII we get later, and now after only listening to it 17,342 times (this is slightly below the mean for U.S. parents with preschool-aged children in 2014), I think this is even better than the sum of IV → iv and III independently, and, in case I haven't demonstrated this already in this email, I fucking love IV → iv.

Elsa the Ice Queen – Let It Go (last chorus)

Let it g[G]o, let it go[D]
[Em]When I'll rise like the break of[C] dawn
Let it [G]go, let it [D]go
That [Em]perfect girl is gon[C]e

[G]Here I sta[D]nd in the [Em]light of d[C]ay [Cm]
[Bm]Let the storm rage [Bb]on,
[C]The cold never bothered me anyway

Incidentally, ending the song on IV, while hardly even a blip in the awesomeness compared to IV → iv → iii → bIII, is a nice touch. For completeness: rounding out the non-diatonics in this song is a VI at the end of the bridge:

Elsa the Ice Queen – Let It Go (bridge)

[D]And one thought crystallizes like an icy blast
[E]I'm never [C]going back,
[D]The past is in t[Am]he past [C]

Also incidentally, if you wondered what it would sound like if Dream Theater covered this (but seriously, this dude is crazy good):

Some Guy on the Internet – Let It Go

And not getting nearly enough credit from three-year-olds is another instant classic from the same soundtrack, "Love is an Open Door":

Anna and Hans – Love is an Open Door

It starts off with a standard I → vi → IV → V, and sets your expectations low, but right before the chorus, we get a II (not really functioning as a secondary dominant here, since it sits between a I and a IV):

Anna and Hans – Love is an Open Door (pre-chorus)

But with [Bm]you I found [D]my place (I see your [D9]face)
And it's n[E]othin' like I've ever known [G7]before

More importantly, this II is followed by another one of my most favoritest things, a big strong dominant seventh in the melody/harmony (on "before"), and another thing we talked about in a recent thread, a spot where intelligent people could easily disagree on which line is the melody. And, if I haven't broken down this one phrase enough, I mentioned a few threads ago how much I love I9's that are more interesting than the sum of their parts (Isus2 and I7); the D9 here totally fits the bill.

Then you're just sure the chorus is going to head back to I → vi → IV → V or similar, especially when it starts with I → vi, but wait!

Anna and Hans – Love is an Open Door (chorus)

Love is an open [D]doo[D/F#]r[E][Gm]
Love is an open [D]doo[D/F#]r[E][Gm]
Love is an open [D]door, with [D/F#]you, with you[E]
[Gm]Love is an open [D]door

How do you like them iv's?!?!

This song also does something we could make a complete thread out of: really clever call-and-response that moves in and out of being synchronized, so it's not quite call and response. A personal favorite example of this:

Hall and Oates – She's Gone

Both: But they could never be
Hall: what she once
Oates: was
Hall: to
Oates: to
Both: me-e-e-e

So, summarizing:

1. You will succumb to kids music.
2. You can make the most of it.
3. When you have two kids between the ages of 3 and 4, you might still find time to write a ~7-page email about the harmonic complexity of Disney music.

-Dan